Typical gas discharge lamps include a small amount of mercury, which is used to excite the discharge that results in the lamp producing light. While mercury performs this function very well, the potential damage to the natural environment and to people that may be caused by mercury is now very well known. Thus, reducing and/or removing mercury from lighting has long been a desired goal.
One alternative to using mercury to excite a discharge is to use a low pressure indium chloride discharge instead of mercury. Under certain conditions, such as the discharge current, the temperature of the indium chloride concentrate, the temperature of the bulb wall, and the type and pressure of the fill gas within the lamp, an indium chloride discharge can effectively replace mercury within a low pressure discharge lamp, with minimal or no loss in lamp efficacy.